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westender



Joined: 02 Aug 2007
Posts: 1261
Location: Portland / Gorge

PostPosted: Sun Mar 25, 2018 11:20 am    Post subject: Reply with quote

My long skinny fins do not prevent my boards from turning on a dime. ?? Not sure why I'm not into swept fins except for my smallest board?
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grantmac017



Joined: 04 Aug 2016
Posts: 920

PostPosted: Sun Mar 25, 2018 11:54 am    Post subject: Reply with quote

Can anyone link to an article or discussion that specifically explains how rake and sweep affect handling?


Weed fins can be a necessary evil, but selecting minimum rake and offset mounting can help. One of the easiest fins I ride is a large weed/wave. It's quite slow but turns well and stays upwind nicely, a whole lot better than a fin trailing a huge patch of grass.
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isobars



Joined: 12 Dec 1999
Posts: 20087

PostPosted: Sun Mar 25, 2018 12:52 pm    Post subject: Reply with quote

jingebritsen wrote:
avoid weed fins. they suck.

I've read that often, but was forced by the exponentially increasing weed invasion in the eastern Gorge to try them anyway*. Like John, I tested fins of all brands professionally many years ago, and have continued testing them (sometimes test 4-5 fins head to head in one day) for my own board fleet to this day. I own well over 100 carefully selected fins (they're dirt cheap -- or even cheaper -- at swap meets, and they have a HUGE impact on board behavior). > 90% of mine are wave and B&J fins, with >90% of those < 26 cm in length.) I value maneuverability first and upwind performance second; top straight line speed is way down my list.

* Holy CRAP am I glad I tried them! In weed-free water, many modern weed-wave fins are every bit as maneuverable as, and rip upwind as well as, my "normal" fins. During the new extended weed season out east ( i.e., early summer well into late fall last year), they outperform "normal" fins hands down in every measure because having a sweatshirt (or even just a string) stuck on your fin usually requires jumping in the water and removing it (that is REALLY slow). In fact I'm now running weed fins on many of my wave and B&J boards full time because many of them outperform many other fins even in weed-free water.

No way am I going to stick to a "normal" fin just because it's normal when there are weed-resistant wavy fins that slash more aggressively, pinch higher and faster with less spinout even in heavy chop, feel no slower in beam reaches, track better, and just flat outsail some of the best "normal" fins I can find for < $200.

But there is a catch: what excels on one board may suck on the next. What lights up one board may suck on some other similar boards. Ya gotta experiment. It makes no sense to pay $2,000 for a board, then dump it for a few hundred bucks because it sucks when all it lacks is a better fin.

BTW, arguably the most useful measure of a fin, unless for some specific niche use like speed trials, is its area. I find that long fins, even if skinny, damp the board's roll rate during sudden rail-to-rail-to-rail transitions from left to right to left, etc. I just don't find them as spontaneous as shorter, lower-aspect-ratio wave and B&J fins.
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cgoudie1



Joined: 10 Apr 2006
Posts: 2377
Location: Killer Sturgeon Cove

PostPosted: Sun Mar 25, 2018 4:06 pm    Post subject: Reply with quote

+1

-Craig

isobars wrote:

BTW, arguably the most useful measure of a fin, unless for some specific niche use like speed trials, is its area. I find that long fins, even if skinny, damp the board's roll rate during sudden rail-to-rail-to-rail transitions from left to right to left, etc. I just don't find them as spontaneous as shorter, lower-aspect-ratio wave and B&J fins.
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Brian_S



Joined: 11 Jun 2005
Posts: 234
Location: SE Michigan

PostPosted: Sun Mar 25, 2018 7:59 pm    Post subject: Reply with quote

d0uglass wrote:
If I put a bigger and more upright than usual fin on my freestyle-wave board I get sore shin muscles. I think it's from the toe-pointing and pressuring of trimming the board and riding off the fin. I also notice that the board isn't as free and surfy in the swells.


Just to add one small thing. When the fin is swept back, like a weed fin or surf fin, the fin becomes less efficient and more 'stable'. By 'stable', I mean that the lift coefficient doesn't change as rapidly with angle of attack. I stole this image from https://aviation.stackexchange.com/questions/22757/what-is-the-reason-for-the-poor-low-speed-characteristics-of-sweptback-wings to illustrate this.:

[/img]

You can put your straight arm out the window while you're driving and feel this. Put your arm straight out and twist your hand slightly up or down. Then sweep your arm back a bit and do the same thing.

On a windsurf board at high speed, a straight upright fin will be faster (less drag) and more 'nervous' for the same area as a swept fin.

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jingebritsen



Joined: 21 Aug 2002
Posts: 3347

PostPosted: Mon Mar 26, 2018 6:00 am    Post subject: Reply with quote

if one is sailing in a venue with an opposing current, one may not perceive how weed fins suck.

if one needs max lift to drag in either flat water blasting or onshore waves, one may perceive exactly as most everyone here on the east coast agrees.

punta san carlos secret: kelp can require weed wave fins. i tried one here in florida conditions: it stank.

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U2U2U2



Joined: 06 Jul 2001
Posts: 5467
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon Mar 26, 2018 9:21 am    Post subject: Reply with quote

grantmac017 wrote:
Can anyone link to an article or discussion that specifically explains how rake and sweep affect handling?


Weed fins can be a necessary evil, but selecting minimum rake and offset mounting can help. One of the easiest fins I ride is a large weed/wave. It's quite slow but turns well and stays upwind nicely, a whole lot better than a fin trailing a huge patch of grass.


The post from the kind Professor from Michigan , illustrates this some. My thoughts have always been that the wings and aerodynamic appendages on aircraft releate partly to fins, or any devices found on watercraft. They Dont tell the entire theory, cause they are in water.

If its known to do what its supposed too; like gravity, Does one need to understand the scientific findings behind it ?
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U2U2U2



Joined: 06 Jul 2001
Posts: 5467
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon Mar 26, 2018 9:31 am    Post subject: Reply with quote

cgoudie1 wrote:
+1

-Craig

isobars wrote:

BTW, arguably the most useful measure of a fin, unless for some specific niche use like speed trials, is its area. I find that long fins, even if skinny, damp the board's roll rate during sudden rail-to-rail-to-rail transitions from left to right to left, etc. I just don't find them as spontaneous as shorter, lower-aspect-ratio wave and B&J fins.


Because weed fins are specialized the area comparison is often not considered.Further THAT very few companies post the area , easy enough to do the math , but in a potential purchase comparison not usually feasible.
Does the area on a weed fin, due to the rake, change in relationship to a pointer of equal area ? My own answer is yes.

CNC fins of OBX are the bomb, yes weed.

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cgoudie1



Joined: 10 Apr 2006
Posts: 2377
Location: Killer Sturgeon Cove

PostPosted: Mon Mar 26, 2018 10:29 am    Post subject: Reply with quote

I'm not a big weed fin fan either (opposing current or not), but occasionally,
they suck less than the alternative (which is continually clearing your fin however
you do it). To me they always feel out of balance and slow. But I really like
a good wave fin, and I've never tried a good weed wave.

Also, I don't mind a good vertical fin, but you have to know what you want
to do with it. If I'm in a drag racing mood(which I might be if there's no
swell), a good vert fin (of appropriate size) is sweet!

So with all this fine advise for the conditions you're in:

A fin too big gives control problems (for me this includes a serious tendency to spin out if I'm over rigged)

A fin too small planes up poorly, and washes out(spins out) with too much back foot pressure and not enough board speed.

1" increments in size changes are meaningful in a similar shape, but the real
determiner for difference in planning is surface area.

A thick fin planes up early and is slow (and harder to spin out)

A thin fin planes late but is fast(er) (and is easier to spin out)

A raked fin is more stable

A vert fin is more efficient (and faster as a result). I find vert fins plenty stable , until they aren't, when they do spin out, they're hard to get to reattach. Raked fins are really easy to get to reattach.

Fin surface irregularities are bad for all sort of reasons. (The worst fin I ever
had for stability was a wave fin, but it was a wave fin with dramatic surface irregularities. Putting dimples in your fin is a bad idea unless they are microscopic).

Weed fins suck, but they suck less that dragging weeds.

Fin design should be matched to sail and board design(you're not getting the best performance from your vertical slalom fin on your rockered wave
board, and a wavey fin in your slalom board probably won't drive it high and fast. Maybe a Swiss army knife Sweeper is your friend ;*)

.04

-Craig
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isobars



Joined: 12 Dec 1999
Posts: 20087

PostPosted: Mon Mar 26, 2018 4:04 pm    Post subject: Reply with quote

jingebritsen wrote:
if one is sailing in a venue with an opposing current, one may not perceive how weed fins suck.

But as you know, I almost never sail in such a venue. I haven't even tried my weed wave fins in that scenario, yet the right ones, even in very small sizes, drive upwind securely, point high, with superb tracking even in massive chop and even when deliberately pushing hard on my back foot as part of my testing. That surprised me greatly, but it's consistent with some weed wave fins. I was even more surprised how precisely they track -- again, consistently -- in extreme full-speed, maximum-g slashes.

HOWEVER, you have ~40-50 pounds on me and there are many incarnations of "weed wave" fins.
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